1. Field of the Invention
The invention relates to a method of producing a profile strip having at one side a raised center area which is at least partially plated with a layer of a metal or a metal alloy, preferably a precious metal or metal alloy.
2. Description of the Prior Art
Such profile strips or wires are used, for example, in the manufacture of contact members wherein the plated sides of the strips become the contacting sides of contact members. The plating layer consists of precious metal or metal alloys to provide for good current conductivity and a high corrosion resistance. The pre-treated contact strip is then usually welded onto a flat carrier member. For good support it should, consequently, have a flat underside or it might have projections extending lengthwise on the strip underside which facilitate welding the strip to such carrier member.
The precious metal layer has to extend over a relatively large area on the raised side of such a profile strip in order to protect the specific contact area, which is about in the center of the profile strip, safely from corrosion, to prevent flaking of the layer at the edges by corrosion and to provide for a relatively wide contact area since the position of the opposite contact is not always properly adjusted. To provide a plating layer only at the predetermined contact area is not sufficient. The same is true, of course, if the contact area is formed not in the center of the contact strip but at its sides.
Such profile strips are usually manufactured by rolling the strip to its desired shape. Precious metal is then selectively deposited on the raised side of the strip. Usually, the precious metal is applied by electroplating, by vapor deposition or by another deposition method. In any case, however, and particularly when electroplated, the deposited layer, that is the precious metal layer, has its greatest thickness in the center of the raised area of the profile strip, that is in cross-section, the layer is sickle-shaped. The metal layer thickness in the center may very well be twice of that at the edges. Since, however, the thickness necessary at the edges would usually be sufficient also for the center contact area, precious metal is deposited in unnecessarily large amounts; that is, it is wasted. Nevertheless, it is difficult to provide by electroplating but also by vapor deposition layers which have the necessary thickness. Usually, the thickness necessary at the edges of the layer is not achieved. It is also disadvantageous that no metal alloys can be deposited by the methods known in the art.
It is also known to first completely plate the metal strips and then to scrape off the unnecessary material to give the strip and the layer thereon the desired shape. This method however is wasteful and very expensive, and consequently, it is usually uneconomical.
It is accordingly desirable to provide a method of producing plated profile strips wherein only the necessary amount of plating material is deposited and the plating material layer has an even thickness over its full width and wherein alloys can be used as plating materials. Also, manufacture of such plated strips should be simple and inexpensive.